LOUISVILLE, Ky. (WDRB) -- An 18-year-old Bullitt Central High School student is in custody after another student reported finding a threatening note at the school in Shepherdsville, Ky., Thursday.

The school was placed on a "soft lockdown" while police investigated, Bullitt County school superintendent Keith Davis said in an emailed statement.

According to a post on the Shepherdsville Police Department's Facebook page, detectives identified and arrested the 18-year-old suspect Thursday afternoon. The post says the student will "undergo a mental health evaluation and face criminal charges."

School district attorney Eric Farris said the student admitted writing the note.

Shepherdsville Police Chief Rick McCubbin said a school resource officer was already at the school when the note was found, and additional officers were called to school on Hwy. 44 in Shepherdsville as a precaution.

Superintendent Keith Davis said the student who wrote the note will face "severe disciplinary action."

Officers investigating the note also found a .22-caliber bullet near a trash can in a classroom. They were not able to determine who put it there. In addition, those officers found a knife in a student's backpack. That student will be disciplined. The two findings were not related to the threatening note, Farris said.

There was no specific threat to the nearby Riverview Opportunity Center building that houses several programs, including an accelerated math and science program, Farris said.